The following U.S. Patents and Applications provide background information and are incorporated herein by reference in entirety.
Various devices and procedures have been developed to assure that an operator of a marine vessel is in a proper position at the helm of the vessel, which are generally referred to as lanyard systems. These lanyard systems vary from simple cords attached between the operator and a kill switch to turn off the marine engine when the operator leaves the helm station to more complex “cordless” systems that use radio signals, infrared technology, or other sensing methodologies to sense the presence of the operator at the helm area.
U.S. Pat. No. 4,250,358 discloses a safety stop switch for a marine engine includes a control unit housing, and a normally closed, single throw toggle switch mounted on the housing and including a switch arm extending away from the housing to permit operation of the switch between closed and open positions. The switch is electrically connected to the engine to interrupt engine operation when switched to the open position. A hood extends from the periphery of the housing and covers the switch arm when in the closed position, and has a peripheral lip which is spaced from the switch arm a dimension which is less than the thickness of a key which encircles the switch arm. A lanyard is connected to the key and to the boat operator, and upon the exertion of a force on the lanyard, the key pulls the switch arm down into the open position, thereby interrupting operation of the marine engine.
U.S. Pat. No. 7,081,028 discloses an engine control system for a marine propulsion system uses a portable control device that is configured to emit first and second signals that are receivable by first and second sensors. The first signal relates to the starting of the engine of the marine propulsion system by the operator. The second signal relates to the presence of the operator, wearing the portable control device, within a predescribed zone surrounding the second sensor near the helm position.
U.S. Pat. No. 7,355,518 discloses a monitoring system detects the presence or absence of a marine vessel operator within a defined zone near the helm of a marine vessel. The detection is accomplished through the use of a provision of an e-field and the detection of e-field strength by a receiving antenna system. When the operator is in the proper helm position, the e-field strength is diminished by the presence of a portion of the operator's body within the e-field zone.
U.S. Pat. No. 6,566,997 discloses a reader unit for use in a radio frequency identification (RFID) system delays the initiation of an interrogation operation when potentially interfering radio frequency (RF) energy is detected within an operational frequency range of the system. The reader unit waits a quasi-random period of time after the detection and then senses the spectral environment again to determine whether the energy is still present. If the energy is still present, the reader unit waits another quasi-random period and the process repeats. If there is no energy present or the energy is below a threshold value, the reader unit immediately initiates the interrogation operation. By delaying the initiation of the interrogation operation until the operative frequency range is free of potential interferers, the likelihood of harmful interference effects is significantly reduced.
U.S. Pat. No. 6,650,227 discloses a reader for an RFID system has an exciter circuit for generating an excitation signal and a feedback circuit coupled to the exciter circuit for automatically tuning the exciter circuit. The exciter circuit has at least one retunable component providing the exciter circuit with adjustable component values and a plurality of signal generating states. The exciter circuit is initially tuned to a first signal generating state, but is retunable to additional signal generating states by adjusting the component value of the retunable component. The feedback circuit includes a circuit evaluator coupled to the exciter circuit for determining a value of an operational parameter of the exciter circuit. A decision-making circuit is coupled to the circuit evaluator for formulating a decision in response to the value of the operational parameter. An adjustment circuit is coupled to the decision-making circuit and exciter circuit for receiving the decision and conveying an adjustment instruction to the exciter circuit in response to the decision.
U.S. Pat. No. 6,476,708 discloses a method is provided for operating an RF transponder system to detect the presence of an RFID device in the proximal space of an RF reader unit having an excitation signal generator circuit and an RFID device detection circuit. The excitation signal generator circuit unit initially operates in a reduced power state, generating ring signals in response to a reduced electrical current and transmitting the ring signals into the proximal space. The RFID device detection circuit evaluates the ring signals to determine variations in an RFID device detection parameter. When the variations pass a variation threshold level due to the presence of the RFID device, the ring signals are terminated and the excitation signal generator circuit switches to an increased power state, wherein the excitation signal generator circuit generates an RF excitation signal which is transmitted to the RFID device.